This invention relates to methods and apparatus for tightening and loosening the jaws of a chuck about a work tool. The invention is particularly suitable for opening and closing the jaws of a drill chuck in reversible drill motors without the use of a key.
There are many types of chucks available for holding a work tool in the machine. Chucks may simply be made from from a collet employing a set screw to hold the tool. Independent chucks are available in which the jaws of the chuck may be set independently of each other. Other chucks employ magnetic forces to hold the work tool in place. Probably the most popular chuck, however, is commonly called the universal chuck or drill chuck. In a drill chuck, the jaws move simultaneously to center the tool in the chuck. This invention is suitable for use with a universal or drill chuck, and is particularly applicable to drills with reversing motors.
In drill chucks, the jaws are caused to clamp or release the work tool because of relative rotary movement between the jaws and the collar external to the jaws. In many drill chucks, rotation of the collar causes a threaded, tapered piece to exert force against the jaws, thus clamping the tool. Typically, drill chucks employ a "key" which is inserted into the chuck and rotated to cause rotary movement of the collar and thus clamp the tool.
This invention is suitable for use with a drill chuck whereby clamping or releasing a tool is achieved by relative rotary movement between the jaws and the drill chuck collar. In the instant invention, however, apparatus is provided so that the tool may be clamped or released without the use of a standard drill chuck key.
Drill chuck keys are generally accepted as a standard device for clamping or releasing a tool within a drill chuck. The use of the drill chuck key, however, has several major drawbacks. First, since the drill chuck key is not attached to the drill itself, the operator must locate the key each time the tool is to be changed. Second, employing a drill chuck key to change tools is difficult or impossible if the operator is in an awkward location. Third, changing the tool with a drill chuck key takes a considerable amount of time and effort.
Consider, for example, an operator assigned the task of drilling a plurality of holes while standing on a conventional ladder. Each time he desires to change the drill bit, he must first locate the key. Assuming he has become tired of climbing down the ladder to locate the key each time a drill bit is to be changed, the operator may decide to tie the key on a string with the other end of the string being tied to a portion of the drill. This practice, however, is often found to be unmanageable since the key and string get wrapped about objects and often reduce the mobility of the operator and may cause an unsafe condition.
Assuming the operator is on the ladder and already has a key, the next step is to insert the key in the chuck to cause rotary movement of the collar. Depending on the dexterity of the operator, the size of the drill, the locking grasp of the jaws to the work tool and other factors, this may be no easy task while the operator is standing on the ladder. If the operator is to break the jaws from the tool or tighten the jaws about the tool with the necessary force, it may require that the operator get down from the ladder so that he can manage turning the key in the chuck. Also, the experienced operator may realize that if he does not firmly grasp the chuck in one hand and the key in the other, he may not achieve proper alignment of the teeth on the key with the teeth on the collar. If the key is not properly aligned, the drill bit may either not be properly grasped by the jaws, or the teeth on the collar or the key may become stripped. Since the operator on the ladder may not safely be able to simultaneously hold the drill, grasp the chuck, and turn the key, or the operator may not be willing to chance that the teeth on the key or chuck may become stripped, the operator may opt for the safest procedure and again climb from the ladder to change the drill bit.
Even if the drill bit can be changed with a drill chuck key while the operator is on the ladder, it is apparent from the above that changing the tool is not necessarily a simple matter. Use of the drill chuck key may result in a considerable amount of time and effort being utilized to change the tool, and this time and effort is multiplied by the number of tool changes required for a given operation.
The instant invention provides methods and apparatus for tightening and loosening the jaws of a drill chuck about a work tool without the use of a key or other tool external to the drill. The disadvantages of a prior art are therefore overcome with the present invention, and novel methods and apparatus are hereinafter provided for easily and rapidly changing tools in a standard drill chuck.